Disk drives are apparatus comprising one or more substantially thin, magnetic disks that are rotated by a spindle motor that is responsive to the drive's control mechanism and associated electronics that communicate data via read and write heads. The disk drives are used in computer systems, such as personal computers, laptop computers and workstation equipped with computer systems, to store large amounts of data, (giga-byte range), in a form that is machine readable for subsequent use by a user. The magnetic disk comprises a surface of magnetizable material having a number of annular regions, called tracks, that extend circumferentially around the disk. Each track is divided into blocks called sectors. To reach a given overall capacity, disk-drives store information and other identification information in the sectors in the form of discrete bits or magnetic transitions written in a concentric manner on the above-mentioned discrete data tracks. The reading and writing of data is accomplished by read and write heads and are positioned over the required track by the drive's positioning control system. The drive's ultimate capacity then, is a function of the number of individual data tracks multiplied by the number of bits written in each track. Current drive formatting techniques will write or encode a fixed, maximum number of bits in each track, hence to reach a given fixed total capacity, the drive will have a fixed number of data tracks. The positioning of these fixed data tracks is determined during a servo-track writing operation. The quantity of data that can be stored on a disk depends upon how much of the surface area is magnetized for the storage of a bit. Ideally, use of the entire disk surface for writing data is a desirable objective. However, the ideal objective is not yet possible.
Current disks used in magnetic disk drives will often have discrete landing and data-zones defined during the disk manufacture. This usually takes the form of a smoother surface in the data-zone to reduce interference between the head & disk during normal drive operation and a rougher surface in the landing-zone to maintain low friction between the head & disk during start-stop operation. Depending on the design, some disks will also have a region of intermediate roughness between the landing and data-zones, usually called the transition-zone. The landing and transition zones are always placed at the inner-radius of the disk with the data-zone extending to the outer edge of the disk. During normal, dynamic operation, the head can encounter a significantly higher level of interference with the disk if it is positioned over the landing zone. This interference can lead to several types of errors during reading & writing, hence there are no data-tracks written into the landing zone and a limited-to-no tracks written in the transition zone.
As briefly stated, during a manufacture process, magnetic hard-disk drives go through a servo-writing operation during which servo information is written on the surface of each disk. This information, is usually in some form of a discrete series of transitions or bursts written at 1/2 track spacing, is used to provide feedback information to the drive electronics to allow accurate positioning of the read/write head elements over a given data track. In general, the servo-writing process is done from disk outer-diameter to inner-diameter with the positioning of the heads controlled by an external, laser-interferometer-based servo-track-writer apparatus.
There are normal positional tolerances that apply to the actual physical location of the landing, transition and data-zones on the disk, additionally there are normal positional tolerances that apply to the actual physical location that the servo-track writer writes the discrete tracks at. To ensure that no data is written in the landing or transition zones, and given that there are the aforementioned tolerances on actual positioning which behave in a statistical manner, there must be a position guardband comprising unused tracks to ensure that in worst case conditions, the last data-track is not written into the transition or landing zone during the servo-write operation, see generally FIG. 1. The position guardband allocated on the disk(s) when servo-writing results in disk drives having an un-used, inner diameter portion located just outside of the transition and landing zones. The actual number of unused track portions can be determined if the statistical distributions of the tolerances are known.
In the above referenced related patent application, Ser. No. 08/831,855, by Wiselogel, a manufacturing process of building a disk drive utilizes a measuring instrument that determines an actual data zone region which comprises an actual distance from an inner diameter head crash stop region to the outer diameter head crash stop region. The process includes computational steps for comparing stored nominal design track density information versus the actual measurement to determine whether there is any extra disk space in the measured region that can be divided among the data tracks in the nominal track distribution to effectively decrease the actual track density of the disk and effectively increase the space used for data. The referenced invention does not address determining the last unused track which can reliably be used as a data-track.
Also in the above referenced related patent application Ser. No. 08/831,856, by Wiselogel, a write inhibit threshold value is adaptively modified for each drive which is based on the actual track pitch that is adaptively controlled during the disk drive manufacturing process taught in Ser. No. 08/831,855, by Wiselogel. The referenced invention does not address determining the last unused track which can reliably be used as a data-track.
Thus, a need is seen to exist for a method for eliminating the position guardband on a disk drive magnetic disk to facilitate utilization of the eliminated guard band portion of the disk for storing data and which method further determines a last data-track in the data zone and facilitates formatting the magnetic disk in accordance with the changed boundaries of the data zone.
A related need is seen to exist for a disk drive apparatus whose magnetic disk media has been manipulated such that the position guardband has been eliminated and which has a data zone with changed boundaries and a last data-track determined to facilitate a magnetic disk formatting arrangement in accordance with the changed boundaries of the data zone.
It is, therefore, a primary object of the present invention to provide a method for eliminating the position guardband and increasing the data zone space on a disk drive magnetic disk to facilitate utilization of the eliminated guardband portion of the disk for storing data and for determining a last data-track in the data zone and facilitating formatting the disk in accordance with the changed boundaries of the data zone.
A related object of the present invention is to provide a disk drive apparatus whose magnetic disk media has been manipulated such that the position guard band portion has been eliminated to facilitate utilization of the eliminated guard band portion of the disk for storing data and which has the last data-track in the data zone determined for facilitating the disk drive apparatus having a disk formatting arrangement in accordance with the changed boundaries of the data zone.